Information processing device and method, program, and information processing system

ABSTRACT

An information processing device, configured to perform color gamut conversion for compressing or enlarging the color gamut of image data, includes: a selecting unit configured to select a plurality of coordinate movement directions to be synthesized for determining the coordinate movement destination of a pixel to be processed during the color gamut conversion; a coordinate moving unit configured to move the coordinates of the pixel to be processed in each of the selected plurality of directions; and a synthesizing unit configured to synthesize coordinate movement in the selected plurality of directions.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention application is a reissue application of U.S. Pat.No. 8,704,846 which issued on Apr. 22, 2014 from U.S. application Ser.No. 12/316,382 filed Dec. 10, 2008, which claims priority from JapanesePatent Application No. JP 2007-321583, filed in the Japanese PatentOffice on Dec. 13, 2007, the entire content contents of which is areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information processing device andmethod, program, and information processing system, and particularlyrelates to an information processing device and method, program, andinformation processing system whereby mapping direction control can berealized in a more flexible manner, with color gamut conversion.

2. Description of the Related Art

Upon image data being exchanged between devices of which the colorexpression regions differ, there is a possibility that out of colorregistration, or hue shift of a high-luminance/high-saturation portionoccurs. Therefore, heretofore, in order to solve such out of colorregistration between devices, color mapping (color gamut conversion),such as compression or enlargement of a color gamut, has been proposed.

SUMMARY OF THE INVENTION

Color gamut conversion is performed by moving (mapping) the coordinatesof a pixel to be processed within color space. Heretofore, with regardto this mapping method, various mapping methods have been proposed.

For example, with the color gamut compression method disclosed inInternational Publication WO 1999/055074 (U.S. Pat. No. 6,560,356), inthe case of compressing the color gamut of a pixel to be processedexisting in a certain hue, one appropriate convergent point is fixed foreach hue, for example, such that a direction destination (convergentpoint) of color gamut compression is set to one point on the Y axishaving the luminance of the maximum saturation point (Cusp point) of anoutput device color gamut 10 such as shown in FIG. 1, thereby performingcompression so as to prevent a tone jump which breaks tone continuityfrom occurrence.

In general, a direction such as shown in FIG. 2 is common as an idealmapping direction of color gamut compression. A high luminance color orlow luminance color is compressed toward a direction where saturation iscompressed as much as possible, i.e., a direction where the color iseliminated, and a color around the Cusp point is compressed toward adirection where the color is somewhat moved to a luminance direction soas to be remained, whereby the appearance of the compression resultsbecomes natural.

Such a compression direction can be realized by employing a method forreferencing a 3DLUT table, or the like.

However, with the method disclosed in International Publication WO1999/055074, there is employed one convergent point for each hue, sothere has been a possibility of difficulty in controlling a mappingdirection in accordance with luminance and saturation subjectively.

There has been recognized demand to enable mapping direction control tobe realized in a more flexible manner by blending multiple mappingdirections which mutually differ with an appropriate ratio to determinea final mapping direction with color gamut conversion, and consequently,enable to a suitable mapping direction to be readily realized dependingon any purpose.

According to an embodiment of the present invention, an informationprocessing device configured to perform color gamut conversion forcompressing or enlarging the color gamut of image data, includes: aselecting unit configured to select multiple coordinate movementdirections to be synthesized for determining the coordinate movementdestination of a pixel to be processed during the color gamutconversion; a coordinate moving unit configured to move the coordinatesof the pixel to be processed in each of the selected multipledirections; and a synthesizing unit configured to synthesize coordinatemovement in the selected multiple directions.

The coordinate moving unit may move the coordinates of the pixel to beprocessed in a saturation direction.

The coordinate moving unit may move the pixel to be processed in arectilinear direction which connects a point, which is disposed on aluminance axis, having the same luminance value as that of the maximumsaturation point, and the pixel to be processed.

The coordinate moving unit may move the pixel to be processed in arectilinear direction which connects a black point and the pixel to beprocessed in a case wherein the luminance of the pixel to be processedis brighter than the luminance of the maximum saturation point, and movethe pixel to be processed in a rectilinear direction which connects awhite point and the pixel to be processed in a case wherein theluminance of the pixel to be processed is darker than the luminance ofthe maximum saturation point.

The selecting unit may select the multiple coordinate movementdirections based on regarding whether or not color enlargementprocessing for enlarging a color gamut is performed as the color gamutconversion.

The selecting unit may select a saturation direction, and a rectilineardirection which connects a black point or white point and the pixel tobe processed as the coordinate movement directions in a case wherein thecolor gamut enlargement processing is not performed, and select asaturation direction, and a rectilinear direction which connects apoint, which is disposed on a luminance axis, having the same luminancevalue as that of the maximum saturation point, and the pixel to beprocessed as the coordinate movement directions in a case wherein thecolor gamut enlargement processing is performed.

The synthesizing unit may synthesize coordinate movement performed inthe selected multiple directions with a ratio based on a blend function.

According to an embodiment of the present invention, an informationprocessing method, which is a color gamut conversion method forcompressing or enlarging the color gamut of image data, includes thesteps of: selecting a plurality of coordinate movement directions to besynthesized for determining the coordinate movement destination of apixel to be processed during the color gamut conversion; moving thecoordinates of the pixel to be processed in each of the selectedplurality of directions; and synthesizing coordinate movement in theselected plurality of directions.

According to an embodiment of the present invention, a program causing acomputer to execute a color gamut conversion method for compressing orenlarging the color gamut of image data, the color gamut conversionmethod includes the steps of: selecting multiple coordinate movementdirections to be synthesized for determining the coordinate movementdestination of a pixel to be processed during the color gamutconversion; moving the coordinates of the pixel to be processed in eachof the selected multiple directions; and synthesizing coordinatemovement in the selected multiple directions.

According to the above configuration, multiple coordinate movementdirections to be synthesized for determining the coordinate movementdestination of a pixel to be processed during the color gamut conversionare selected, the coordinates of the pixel to be processed is moved ineach of the selected multiple directions, and coordinate movementperformed in the selected multiple directions are synthesized.

According to an embodiment of the present invention, an informationprocessing system in which a supply-side device transmits image data toan obtaining-side device, and performs color gamut conversion forcompressing or enlarging the color gamut of the image data, thesupply-side device includes a supplying unit configured to supply theimage data to the obtaining-side device, and the obtaining-side deviceincludes an obtaining unit configured to obtain the image data suppliedfrom the supply-side device, a selecting unit configured to selectmultiple coordinate movement directions to be synthesized fordetermining the coordinate movement destination of a pixel to beprocessed during the color gamut conversion as to the obtained imagedata, a coordinate moving unit configured to move the coordinates of thepixel to be processed in each of the selected multiple directions, and asynthesizing unit configured to synthesize coordinate movement in theselected multiple directions.

According to the above configuration, with an information processingsystem in which a supply-side device transmits image data to anobtaining-side device, and performs color gamut conversion forcompressing or enlarging the color gamut of the image data, with thesupply-side device, the image data is supplied to the obtaining-sidedevice, and with the obtaining-side device, the image data supplied fromthe supply-side device is obtained, multiple coordinate movementdirections to be synthesized for determining the coordinate movementdestination of a pixel to be processed during the color gamut conversionas to the obtained image data are selected, the coordinates of the pixelto be processed are moved in each of the selected multiple directions,and coordinate movement performed in the selected multiple directions issynthesized.

According to an embodiment of the present invention, an informationprocessing system in which a supply-side device transmits image data toan obtaining-side device, and performs color gamut conversion forcompressing or enlarging the color gamut of the image data, thesupply-side device includes a selecting unit configured to selectmultiple coordinate movement directions to be synthesized fordetermining the coordinate movement destination of a pixel to beprocessed during the color gamut conversion as to the obtained imagedata, a coordinate moving unit configured to move the coordinates of thepixel to be processed in each of the selected multiple directions, asynthesizing unit configured to synthesize coordinate movement in theselected multiple directions, and a supplying unit configured to supplythe image data of which the coordinates are moved in the direction wherethe multiple directions are synthesized, subjected to the color gamutconversion, to the obtaining-side device, and the obtaining-side deviceincludes an obtaining unit configured to obtain the image data subjectedto the color gamut conversion, supplied from the supply-side device.

According to the above configuration, with an information processingsystem in which a supply-side device transmits image data to anobtaining-side device, and performs color gamut conversion forcompressing or enlarging the color gamut of the image data, with thesupply-side device, multiple coordinate movement directions to besynthesized for determining the coordinate movement destination of apixel to be processed during the color gamut conversion as to the imagedata are selected, the coordinates of the pixel to be processed aremoved in each of the selected multiple directions, coordinate movementperformed in the selected multiple directions are synthesized, and theimage data of which the coordinates are moved in the direction where themultiple directions are synthesized, subjected to the color gamutconversion, is supplied to the obtaining-side device, and with theobtaining-side device, the image data subjected to the color gamutconversion, supplied from the supply-side device is obtained.

The term “network” as used here means an arrangement wherein at leasttwo devices are connected, whereby transmission of information can beperformed from a certain device to the other device. The devices whichcommunicate through the network may be separate devices, or may beinternal blocks making up one device.

Also, the term “communication” may include not only wirelesscommunication and cable communication but also communication whereinwireless communication and cable communication are mixed, i.e., wirelesscommunication is performed within a certain section, and cablecommunication is performed within another section. Further, anarrangement may be made wherein communication from a certain device tothe other device is performed by cable communication, and communicationfrom the other device to a certain device is performed by wirelesscommunication.

According to embodiments of the present invention, color gamutconversion can be performed. Particularly, a more suitable mappingdirection can be readily realized according to a purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a coordinate moving situation exampleaccording to the color gamut conversion with the related art;

FIG. 2 is a diagram illustrating a coordinate moving situation exampleaccording to ideal color gamut conversion;

FIG. 3 is a block diagram illustrating a configuration example of acolor gamut conversion device to which an embodiment of the presentinvention has been applied;

FIG. 4 is a block diagram illustrating a detailed configuration exampleof a mapping processing unit;

FIG. 5 is a flowchart for describing a flow example of color gamutconversion processing;

FIG. 6 is a schematic view illustrating a format example of color gamutinformation;

FIG. 7 is a schematic view illustrating another format example of colorgamut information;

FIGS. 8A and 8B are schematic views illustrating a color gamut example;

FIGS. 9A and 9B are schematic views illustrating yet another formatexample of color gamut information;

FIGS. 10A and 10B are schematic views illustrating yet another formatexample of color gamut information;

FIG. 11 is a schematic view for describing a situation example of colorgamut compression;

FIG. 12 is a schematic view for describing a situation example of colorgamut enlargement;

FIG. 13 is a diagram illustrating an example of a Cusp table forsaturation;

FIG. 14 is a diagram illustrating a saturation ratio example;

FIG. 15 is a diagram illustrating an LU table example;

FIG. 16 is a diagram illustrating another LU table example;

FIG. 17 is a graph illustrating an example of a compressing directionmapping function;

FIG. 18 is a graph illustrating an example of an enlarging directionmapping function;

FIG. 19 is a schematic view illustrating a saturation calculation methodexample;

FIG. 20 is a schematic view wherein a color gamut clip situation and acolor gamut compression situation are compared;

FIG. 21 is a schematic view illustrating a virtual clip boundaryexample;

FIG. 22 is a flowchart for describing a flow example of blend mappingprocessing;

FIG. 23 is a diagram for describing a situation of C-direction mappingprocessing;

FIG. 24 is a diagram for describing a situation of Cusp-directionmapping processing;

FIG. 25 is a diagram for describing a situation of BW-direction mappingprocessing;

FIG. 26 is a diagram illustrating a difference example of each ofmapping directions;

FIG. 27 is a schematic view illustrating a blend situation example;

FIG. 28 is a diagram illustrating a blend function example;

FIG. 29 is a diagram illustrating a blend function example;

FIG. 30 is a diagram illustrating a mapping example;

FIGS. 31A and 31B are block diagrams illustrating a configurationexample of an information processing system to which an embodiment ofthe present invention has been applied; and

FIG. 32 is a block diagram illustrating a configuration example of apersonal computer to which an embodiment of the present invention hasbeen applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 3 is a block diagram illustrating a principal configuration exampleof a color gamut conversion device to which an embodiment of the presentinvention has been applied.

A color gamut conversion device 100 shown in FIG. 3 is an informationprocessing device wherein the color gamut of input picture content datais converted based on original color gamut information and target colorgamut information, thereby obtaining output picture content data. Thecolor gamut conversion device 100 includes a format conversion unit 101,maximum saturation point calculating unit 102, and color conversionprocessing unit 103 as a principal configuration.

The format conversion unit 101 converts input picture content data madeup of image data, e.g., from YCC data (Yi, Cbi, Cri) to YCH data (Yi,Ci, Hi) made up of luminance, saturation, and hue so as to prevent hueshift from occurrence due to color gamut conversion. Thus, convertinginto the YCH data enables color gamut conversion (coordinate movement)to be performed for each hue (on a plane), whereby occurrence of hueshift due to color gamut conversion can be suppressed.

Based on target color gamut information indicating a target color gamutwhich is the color gamut of the conversion destination of the originalcolor gamut which is a color gamut to which the input picture contentdata belongs (a color gamut including a color distribution of all of thepixels in the input picture content data, which has been employed forgeneration of the input picture content data), the maximum saturationpoint calculating unit 102 calculates all of the YC coordinatesinformation (Ycp, Ccp) of the maximum saturation point for each hue (Hi)(hereafter, also referred to “Cusp point”), of the target color gamutthereof. A white point and black point are fixed, so a target colorgamut for each hue Hi is determined by determining the Cusp point.

Note that with the present Specification, YC coordinates are representedwith (coordinate in the luminance direction (Y), coordinate in thesaturation direction (C)). For example, when the YC coordinates of acertain point are (Y1, C1), the coordinate in the luminance (Y)direction of this point is Y1, and the coordinate in the saturation (C)direction is C1.

The color conversion processing unit 103 converts (compresses orenlarges) the color of each pixel of the input picture content databelonging to the original color gamut into a color of the target colorgamut to obtain output picture content data. The color conversionprocessing unit 103 includes an LU-boundary specifying unit 111,transform function defining unit 112, virtual clip boundary determiningunit 113, and mapping processing unit 114.

The LU-boundary specifying unit 111 specifies whether tocoordinate-convert (map) which range of a color gamut into which rangeat the time of color gamut conversion (color gamut compression or colorgamut enlargement), i.e., specifies a mapping source region and mappingdestination region. The transform function defining unit 112 defines acolor gamut conversion function. The virtual clip boundary determiningunit 113 determines a boundary serving as a movement destinationcandidate for each pixel to be processed (virtual clip boundary) basedon the transform function defined by the transform function definingunit 112. The mapping processing unit 114 performs mapping processingwherein each pixel to be processed is moved onto the virtual clipboundary determined by the virtual clip boundary determining unit 113.

FIG. 4 is a block diagram illustrating a detailed configuration exampleof the mapping processing unit 114 in FIG. 1. As shown in FIG. 4, themapping processing unit 114 includes a combination selecting unit 121,C-direction mapping processing unit 122, Cusp-direction mappingprocessing unit 123, BW-direction mapping processing unit 124, synthesisprocessing unit 125, and format conversion unit 126.

The combination selecting unit 121 selects a combination in a mappingdirection to be synthesized (blended) for determining the coordinatemovement destination of a pixel to be processed during color gamutconversion, from multiple coordinate movement directions (mappingdirections) prepared beforehand. The C-direction mapping processing unit122 through BW-direction mapping processing unit 124 perform mapping ina mutually different predetermined direction (fixed mapping direction).That is to say, the combination selecting unit 121 selects multiplemapping directions to be blended by selecting multiple processing unitsfor executing mapping processing from the C-direction mapping processingunit 122 through BW-direction mapping processing unit 124.

The C-direction mapping processing unit 122 performs mapping processingin a fixed direction wherein the pixel to be processed is moved in asaturation direction (C direction) on luminance and saturation planes.The Cusp-direction mapping processing unit 123 performs mappingprocessing in a fixed direction wherein the pixel to be processed ismoved in a rectilinear direction which connects a point having the sameluminance value (Ycp) as that of the maximum saturation point (Cusppoint) on the luminance (Y) axis, i.e., a point (Ycp, 0) in the YCcoordinates and the pixel to be processed, with the luminance andsaturation plane. That is to say, the point (Ycp, 0) on the YCcoordinates is regarded as a convergent point. The BW-direction mappingprocessing unit 124 performs mapping processing in a fixed directionwherein the pixel to be processed is moved in a rectilinear directionwhich connects a black point and the pixel to be processed in a casewherein the luminance of the pixel to be processed is brighter than thatof the Cusp point, and the pixel to be processed is moved in arectilinear direction which connects a white point and the pixel to beprocessed in a case wherein the luminance of the pixel to be processedis darker than that of the Cusp point, on the luminance and saturationplanes.

That is to say, the C-direction mapping processing unit 122 throughBW-direction mapping processing unit 124 perform the coordinate movement(mapping) of the pixel to be processed in the direction selected by thecombination selecting unit 121.

The synthesis processing unit 125 obtains each mapping processing resultsupplied from the C-direction mapping processing unit 122 throughBW-direction mapping processing unit 124 which have performed mappingprocessing, and synthesizes (blends) each mapping direction with a ratiobased on a blend function, thereby determining the final movementdestination (mapping point) of the pixel to be processed. The formatconversion unit 126 converts the coordinates of the mapping point, forexample, from the YCH coordinates to the YCC coordinates.

Next, description will be made regarding a flow example of color gamutconversion processing executed by the color gamut conversion device 100,with reference to the flowchart in FIG. 5. Description will be made withreference to FIGS. 6 through 21, as appropriate.

Upon the color gamut conversion processing being started, in step S101the format conversion unit 101 performs calculations, for example, suchas shown in the following Expressions (1) through (4) so as not to causehue shift due to color gamut conversion, and converts the format ofinput content data, for example, from the YCC to YCH (converts thecoordinates system from the YCC coordinates to YCH coordinates).

$\begin{matrix}{{Yi} = {Yi}} & (1) \\{{Ci} = \sqrt{{Cbi}^{2} + {Cri}^{2}}} & (2) \\{{\text{if~~}{Cri}} > 0} & (3) \\{{Hi} = {{arc}\;{\tan\left( \frac{Cri}{Cbi} \right)} \times \frac{180}{\pi}}} & \; \\\text{else} & \; \\{{Hi} = {{{arc}\;{\tan\left( \frac{Cri}{Cbi} \right)} \times \frac{180}{\pi}} + 360}} & (4)\end{matrix}$

Upon the format being converted, in step S102 the maximum saturationpoint calculating unit 102 calculates the YC coordinates information(Ycp, Ccp) of the maximum saturation point (Cusp point) of each hue Hibased on the target color gamut information.

The target color gamut information and original color gamut informationare assumed to be transmitted/received by communication, for example, asthe meta data of picture content data. Accordingly, for example, it isvery important that the volume of such information is not great, suchinformation can be readily described, and so forth. A specific examplewill be shown below.

FIG. 6 is a schematic view illustrating a format example of color gamutinformation. As shown in Table 141 in FIG. 6, several pieces of colorgamut information which are frequently used is prepared beforehand, andindexes corresponding thereto are prepared. Only the index numeric valuedata thereof is transmitted/received by communication, therebyexchanging color gamut data. For example, if color gamut information tobe transmitted is implicated beforehand, such as shown in FIG. 6, whendesiring to transmit Wide RGB color gamut information, a numeric value“2” alone has to be transmitted. It goes without saying that this indexmay not be a numeric value, so may be a character such as an alphabet ora symbol, for example.

With this format, communication load can be reduced since the volume ofdata to be exchanged is small, but it is commonly difficult to definethe color gamut inherent in each output device beforehand, andaccordingly, exchange of representative color gamut data is performedconsistently. Also, a reception side which has obtained an index has torender the received information into color gamut information having aform which can be employed for internal color gamut compression(later-described Cusp table, or the like).

FIG. 7 is a schematic view illustrating another format example of colorgamut information. As shown in Table 142 in FIG. 7, in a case wherein adevice which desires to express a color gamut is, for example, a displaydevice for displaying an image, there can be calculated a transformationmatrix for transforming a color which can be expressed by the displaydevice as long as the color is xy chromaticity data of three primarycolors, red, blue, green, and white point into a numeric value of colorspace which does not depend on any device (XYZ, CIELAB, etc.). That isto say, a color gamut can be defined with RGB. In the case of a displaydevice of three colors or more, a color gamut is chromaticityinformation of all of the primary colors serving as the basis thereof.This format provides excellent approximation to a display device whereinadditive color mixing properties hold, but is employed as approximationregarding other devices. Also, in the same way as the case shown in FIG.6, the information has to be rendered into color gamut information whichcan be employed for color gamut compression internally on the receptionside (such as a later-described Cusp table).

As shown in FIG. 8A, when expressing the color gamut of a certain devicewith YCC (Y, Cb, Cr) space (color gamut 143), as shown in FIG. 8B, a cutplane cut with an iso-hue plane can be represented with aYC2-dimensional plane wherein the vertical axis is luminance Y, and thehorizontal axis is saturation C (color gamut 144). A color gamut shapeon this plane can be approximated with a triangle connecting a whitepoint, black point, and Cusp point such as the color gamut 144 shown inFIG. 8B as long as the YC coordinates of the maximum saturation point(Cusp) is understood. The color gamut 143 of the device can be definedapproximately by making use of this feature as long as the YCcoordinates of the Cusp point (Cusp information) on severalrepresentative hue planes is held as a numeric-value table. Such a tableof the YC coordinates (Cusp information) of the maximum saturation point(Cusp) of a representative hue is referred to as a Cusp table. Thevolume of the Cusp table depends on the number of held representativehues, but particularly, the color gamut of a display device or the likecan be approximated with sufficient excellent precision by the Cusptable made up of Cusp coordinates regarding six hues of red (R), green(G), blue (B), cyan (C), magenta (M), and yellow (Y).

Table 145 shown in FIG. 9A and Table 146 shown in FIG. 9B are Cusptables (representative six hues) of sRGB color gamut in sYCC space. sYCCis luminance color difference separated space derived from RGB definedfor high-vision by employing ITU-R BT. 601 which is internationalstandard of a transformation matrix to YCC, and is color space which iswider than sRGB in which the actual situation of the color gamut of thedisplay is reflected, and covers an output-side device such as a printeror the like. The coordinates of the Cusp point in this case (Cuspinformation) may be represented with YCH (luminance, saturation, hue)coordinates such as shown in Table 145 shown in FIG. 9A, or may berepresented with YCbCr (luminance, color difference information)coordinates such as shown in Table 146 shown in FIG. 9B. The Cuspinformation of hues other than representative hues can be obtained withlinear interpolation or the like from the Cusp information of theneighborhood thereof.

The luminance, color difference, hue, saturation information employedhere are not restricted to the YCC space, and information conforming toluminance, color difference, hue, saturation information in otherluminance and color difference space (e.g., CIELAB, CIELUV, etc.) may beemployed.

Note that a hue to be set as a representative hue is arbitrary, and forexample, may also be set with a certain hue interval. Table 147 shown inFIG. 10A is a Cusp table which represents Cusp information with the YCHcoordinates wherein a representative hue is set for each degree, andTable 148 shown in FIG. 10B is a Cusp table which represents Cuspinformation with the YCbCr coordinates wherein a representative hue isset for each degree similarly. If an arrangement is made wherein such aCusp table itself can be exchanged by communication as color gamutinformation, received color gamut information can be used as is at thetime of color gamut compression on the reception side. Also, hues havean equal interval, so a reference method is easy. Such a Cusp table hasfeatures wherein if the hue interval is set great, the informationvolume gets smaller, and if the hue interval is set small, theinformation volume gets greater. It is desirable to determine theoptimal interval while taking load and precision oftransmission/reception of information into consideration. Also, whenexchanging a Cusp table, handling processing can be readily realizedsuch that hues are thinned out, and are then transmitted depending on asituation. The Cusp information of hues other than representative huesis obtained with linear interpolation or the like from the Cuspinformation of the neighborhood thereof.

In this case as well, the employed luminance, color difference, hue,saturation information are not restricted to the YCC space, andinformation conforming to luminance, color difference, hue, saturationinformation in other luminance and color difference space (e.g., CIELAB,CIELUV, etc.) may be employed.

As described above, an original color gamut and target color gamut canbe exchanged in various formats, but for example, in a case whereintarget color gamut information is given in a form such as a Cusp tablewhich is table information made up of the YC coordinates of the Cusppoint according to representative hues, the maximum saturation pointcalculating unit 102 employs the Cusp table thereof to calculate the YCcoordinates information (Ycp, Ccp) of the Cusp point of a desired huefrom the YC coordinates of the Cusp point of a nearby representative huewith linear interpolation or the like. Also, for example, in a casewherein target color gamut information is given with chromaticityinformation or the like, a Cusp table can be generated from thechromaticity information thereof with internal calculation, and themaximum saturation point calculating unit 102 can also obtain the YCcoordinates information (Ycp, Ccp) of the Cusp point with reference tothe Cusp table thereof. Upon the YC coordinates of the Cusp point beingdetermined, a color gamut on the YC plane at the hue Hi is determined.

Note that, for example, in a case wherein output picture content data isrecorded in a recording medium, when no communication can be performedwith an output device for outputting the output picture content data, orwhen there are multiple devices available as output devices, which havea mutually different color gamut, there are conceived a case wherein thetarget color gamut information is not obtained, and a case wherein thetarget color gamut information is not uniquely determined. Thus, in acase wherein a target color gamut is unidentified or undetermined, themaximum saturation point calculating unit 102 may set predeterminedcolor gamut information as tentative target color gamut information, forexample. Note that, in this case, it is desirable to employ a commoncolor gamut such as sRGB or sYCC as a color gamut to be set as tentativetarget color gamut information so as to be compatible with many moredevices.

The following processing is performed similarly not only as to targetcolor gamut information but also as to tentative target color gamutinformation. Accordingly, in the following, target color gamutinformation and tentative target color gamut information will not bedistinguished, and both will be described as target color gamutinformation unless differentiation is appropriate.

Now, description will be back to FIG. 5. In step S103, the LU-boundaryspecifying unit 111 specifies a non-mapping boundary and mapping limitboundary. Now, attention is paid to a compression ratio in a saturationdirection.

FIG. 11 is a schematic view illustrating a situation of color gamutconversion in the case of compressing a color gamut. In FIG. 11, aregion surrounded with a thick line (region surrounded with a triangleof which the peaks are a white point, black point, and Cusp point) is afinal compression destination region (target compressed area), i.e., atarget color gamut. A T-boundary (Target boundary) 151 is an edge(boundary) other than the Y axis of this target region. With theT-boundary 151 as reference, a boundary somewhat smaller in thesaturation direction is a non-mapping boundary (U-boundary (Uncompressedboundary)) 152. A region surrounded with the Y axis and the U-boundary152 is a non-mapping region, and pixels included in this region are notsubjected to color gamut compression (coordinate movement). Next, howmuch region should be compressed into a compression destination regionhas to be specified. A boundary line for specifying whether the color ofa picture content is expanded to how much color gamut is a mapping limitboundary (L-boundary (Limited boundary)) 153. With color gamutcompression, the L-boundary 153 becomes a boundary line enlarged in thesaturation direction as compared to the T-boundary 151. That is to say,color gamut compression means to compress a region surrounded with theU-boundary 152 and L-boundary 153 into a region surrounded with theU-boundary 152 and T-boundary 151.

When expressing this only in the saturation direction, according to thiscolor gamut compression, the coordinates of a0in in FIG. 11 are moved toa0out, for example. Note that all of the colors having a highersaturation than that of the L-boundary 153 are clipped in the T-boundary151 (subjected to coordinate movement onto the T-boundary 151). Forexample, the coordinates of a1in in FIG. 11 are moved to a1out.

FIG. 12 is a schematic view illustrating a situation of color gamutconversion in the case of enlarging a color gamut. The case ofenlargement differs from the case of compression in that the L-boundary153 becomes a boundary line reduced in the saturation direction ascompared to the T-boundary 151. That is to say, color gamut enlargementmeans to enlarge a region surrounded with the U-boundary 152 andL-boundary 153 to a region surrounded with the U-boundary 152 andT-boundary 151.

When expressing this only in the saturation direction, according to thiscolor gamut enlargement, the coordinates of a0in in FIG. 12 are moved toa0out, for example. Note that all of the colors having a highersaturation than that of the L-boundary 153 are clipped in the T-boundary151 (subjected to coordinate movement onto the T-boundary 151). Forexample, the coordinates of a1in in FIG. 12 are moved to a1out.

The L-boundary 153 and U-boundary 152 are set as a saturationenlargement ratio or saturation reduction ratio when setting thesaturation of the T-boundary 151 to “1”. There can be conceived varioussetting methods, but a constant value may be employed regardless ofhues, or a setting value may also be changed for each hue. On the otherhand, in the case of changing the values of the L-boundary 153 andU-boundary 152 for each hue, a so-called LU table is defined. This istable information including the values of the L-boundary 153 andU-boundary 152 for each hue, whereby there can be specified regardingwhether color gamut mapping performed with the hue thereof is colorgamut compression or color gamut enlargement in accordance with thevalue of the L-boundary 153.

When there is original color gamut information, the expanded level ofthe color in the saturation direction of a picture content can beunderstood, so the L-boundary 153 can be determined by referencing theoriginal color gamut information. Now, let us assume that a Cusp tablefor the saturation (C) of an original color gamut and target color gamutis in a state such as shown in the graph in FIG. 13. Upon the value ofthe original color gamut being divided by the value of the target colorgamut, there can be obtained the saturation ratio of the Cusp point ofthe original color gamut as to the target color gamut for each hue suchas a graph shown in FIG. 14.

A portion of which the saturation ratio is smaller than 1.0 means thatthe target color gamut is wider than the original color gamut, and insuch a case, color gamut mapping to be performed is color gamutenlargement.

Next, the mapping limit boundary (L-boundary) 153 is defined for eachhue, but the saturation ratio itself of each hue shown in FIG. 15 can bedefined as the mapping limit boundary (L-boundary) 153, for example.

Also, the non-mapping boundary (U-boundary) 152 is defined for each hue,but there can be conceived various methods for determining thenon-mapping boundary (U-boundary) 152. For example, an arrangement maybe made wherein when a region to be compressed or enlarged is great, amapping destination region is also assumed to be somewhat great, andwhen the region to be compressed or enlarged is small, the mappingdestination region is also assumed to be small, thereby determining theU-boundary 152 so as to maintain a certain level of the region ratiothereof. For example, an arrangement may be made wherein the U-boundary152 (saturation reduction ratio) is a half of the L-boundary 153(saturation enlargement ratio) at the time of color gamut compression,and the U-boundary 152 (saturation reduction ratio) is the color gamutreduction ratio which is double the L-boundary 153 (saturationenlargement ratio) at the time of color gamut enlargement. In this case,for example, if we say that a saturation ratio such as shown in FIG. 14is given as the L-boundary 153, an LU table such as shown in FIG. 15 isgenerated.

Note that, for example, there is a color gamut conversion method whereinonly color gamut compression for colors outside the target color gamutis performed, and color gamut enlargement for colors within the targetcolor gamut is not performed. In the case of such a color gamutconversion method, an LU table such as shown in FIG. 16 can be obtained,for example. With the saturation ratio for each hue of the Cusp point,of the saturation ratio for each hue shown in FIG. 14, a portion ofwhich the value is less than “1”, and is fixed to “1.0” is employed asthe L-boundary 153, the U-boundary 152 is obtained based on theL-boundary 153, thereby generating an LU table as described above.

Now description will be back to FIG. 5. In step S104, the transformfunction defining unit 112 defines a transform function. Upon acompression situation when assuming that the setting value of theU-boundary 152 is “0.75”, and the setting value of the L-boundary 153 is“1.5” being represented with a function, a curve 161 shown in FIG. 17 isobtained. This curve 161 will be referred to as a mapping function. Arange of which the inclination is “1” indicates a non-mapping region.Color gamut compression indicates that a range surrounded with theU-boundary 152 and L-boundary 153 on the horizontal axis is compressedto obtain a range surrounded with the U-boundary 152 and T-boundary 151on the vertical axis. The compression method at this time is arbitrary,and there are conceived various methods. For example, a solid line 161Adenotes linear compression. A dashed line 161B is an example wherein thefunction is bent smoothly so as to be compressed gradually. A single-dotbroken line 161C denotes not compression but a color gamut clip as tothe T-boundary 151.

That is to say, according to the form of the curve 161 within thisrange, for example in FIG. 11, there is determined the ratio (r:s)between the distance to the T-boundary 151 and distance to theU-boundary 152 of the a0out which is the movement destination of thea0in wherein the ratio between the distance to the L-boundary 153 andthe distance to the U-boundary 152 is p:q. In other words, the function(compression function) indicated with the curve 161 indicates acompression ratio (R_ccomp) in the saturation direction of a certainpixel to be processed, and the virtual clip boundary of the pixel to beprocessed is determined according to the output value of this function.

The mapping function is determined depending on the values of theL-boundary 153 and U-boundary 152, so if the values of the L-boundary153 and U-boundary 152 are changed for each hue, the mapping function isalso changed. Now, let us say that a numeric value “0.8” which is lessthan “1.0” is given to the L-boundary 153, and the U-boundary 152 is“0.7”, mapping in this case is enlargement processing. The situation ofthe mapping function in this case is shown in a curve 162 in FIG. 18. Inthe same way as in the case of the curve 161, a range of which theinclination is “1” denotes a non-mapping region. A solid line 162A meanslinear enlargement. A dashed line 162B is an example wherein enlargementis performed gradually.

That is to say, according to the form of the curve 162 within thisrange, for example in FIG. 11, there is determined the ratio (r:s)between the distance to the T-boundary 151 and distance to theU-boundary 152 of the a0out which is the movement destination of thea0in wherein the ratio between the distance to the L-boundary 153 andthe distance to the U-boundary 152 is p:q. In other words, the function(enlargement function) indicated with the curve 162 indicates anenlargement ratio (R-ccomp) in the saturation direction of a certainpixel to be processed, and the virtual clip boundary of the pixel to beprocessed is determined according to the output value of this function.

Now, description will be back to FIG. 5. In step S105, the virtual clipboundary determining unit 113 determines a virtual clip boundary.

The virtual clip boundary determining unit 113 employs the saturation Ciof the pixel to be processed to reference the transform function(compression function or enlargement function) defined by the processingin step S104. However, the transform function is a value obtained bynormalizing the saturation at the T-boundary 151 with “1”, so saturationCi_c at the T-boundary 151 having the same luminance as that of thepixel to be processed has to be obtained. For example, as shown in FIG.19, if we say that the YC coordinates of the pixel to be processed is(Yi, Ci), the saturation Ci_c at the T-boundary 151 having the sameluminance as that of the pixel to be processed can be obtained as thesaturation of an intersection point between a straight line connecting awhite point and Cusp point, and a straight line connecting the pixel tobe processed (Yi, Ci) and the luminance point (Yi, 0) of the pixel to beprocessed on the Y axis.

Saturation Ci_norm for referencing the compression function can becalculated such as shown in the following Expression (5) by employingthe saturation Ci_c of this intersection point and the saturation Ci ofthe pixel to be processed.

$\begin{matrix}{{Ci\_ norm} = \frac{Ci}{Ci\_ c}} & (5)\end{matrix}$

For example, the virtual clip boundary determining unit 113 employs thissaturation Ci_norm to reference the compression function indicated bythe curve 161 in FIG. 17, and determines the compression ratio R_ccompin the saturation direction of the pixel to be processed. Upon theR_ccomp being determined, the virtual clip boundary (V-boundary (Virtualclip boundary)) of the pixel to be processed can be determined. Thus,the virtual clip boundary (V-boundary) is determined, whereby colorgamut compression can be conceived as processing for repeatedlyperforming color gamut clip.

A in FIG. 20 is a schematic view illustrating a color gamut clipsituation. Color gamut clip denotes, as shown in A in FIG. 20, that acolor outside the target color gamut is moved onto the T-boundary 151which is the boundary of the target color gamut (clipped in theT-boundary 151). For example, in A in FIG. 20, a pixel to be processedshown in a white circle is subjected to coordinate movement to a clippoint on the T-boundary 151 shown in a filled circle.

B in FIG. 20 is a schematic view illustrating a color gamut compressionsituation. As described above, color gamut compression means to move apixel to be processed onto the virtual clip boundary (V-boundary)corresponding to the pixel to be processed thereof. For example, in B inFIG. 20, a pixel to be processed 181 is subjected to coordinate movementto a clip point 182 on a V-boundary 191A, and a pixel to be processed183 is subjected to coordinate movement to a clip point 184 on aV-boundary 191B. That is to say, color gamut compression can be regardedas equivalent to performing the same processing as that in the case of acolor gamut clip in A in FIG. 20 for each pixel to be processed.

For example, upon description being made regarding the Cusp point, theYC coordinates (Ycp, Ccp_V) of a clip point Cusp_V of the Cusp point ofthe YC coordinates (Ycp, Ccp) can be calculated such as the followingExpression (6) by employing the compression ratio R_ccomp in thesaturation direction.Cusp_V=(Ycp,Ccp_V)=(Ycp,R_ccomp×Ccp)  (6)

A virtual clip boundary (V-boundary) 191 is determined from the YCcoordinates of the clip point Cusp_V. For example, as shown in FIG. 21,the virtual clip boundary (V-boundary) 191 of the Cusp point is made upof a line segment with the clip point Cusp_V and a white point as bothends, and a line segment with the clip point Cusp_V and a black point asboth ends.

That is to say, the V-boundary 191 is determined with theabove-mentioned compression function, and the ratio (p:q) between thedistance to the L-boundary 153 and the distance to the U-boundary 152 ofa pixel to be processed. In other words, pixels to be processed havingthe same ratio (p:q) between the distance to the L-boundary 153 and thedistance to the U-boundary 152 share the V-boundary 191.

Note that description has been made so far regarding the case ofcompressing a color gamut, but the method for determining the V-boundary191 in the case of enlarging a color gamut is basically the same as thatin the case of compressing a color gamut.

Now, description will be back to FIG. 5. In step S106, the mappingprocessing unit 114 executes blend mapping processing wherein each pixelto be processed is mapped (subjected to coordinate movement) on theV-boundary 191 corresponding to each pixel to be processed determinedsuch as described above, in a direction where multiple mappingdirections are blended. A detailed processing flow example of this blendmapping processing will be described later.

Upon the processing in step S106 being ended, the color gamut conversiondevice 100 ends the color gamut conversion processing. As describedabove, the color gamut conversion device 100 converts a color gamut froman original color gamut to a target color gamut appropriately.

Next, a flow example of the blend mapping processing executed in stepS106 in FIG. 5 will be described with reference to the flowchart in FIG.22. Description will be made with reference to FIGS. 23 through 30 asappropriate.

Upon the blend mapping processing being started, in step S121 thecombination selecting unit 121 determines whether or not both of thecolor gamut compression processing and color gamut enlargementprocessing are performed regarding input picture content data to besubjected to color gamut conversion as color gamut conversion. At thistime, the combination selecting unit 121 references the LU table todetermines whether or not the enlargement processing is performeddepending on regarding whether or not there is a value less than 1 inthe values of the L-boundary 153. In a case wherein determination ismade that the enlargement processing is also performed, the combinationselecting unit 121 selects the C-direction mapping processing unit 122and Cusp-direction mapping processing unit 123, and advances theprocessing to step S122.

In step S122, the C-direction mapping processing unit 122 executesC-direction mapping processing wherein a pixel to be processed is moved(mapped) onto the virtual clip boundary (V-boundary) 191 in thesaturation (C) direction.

FIG. 23 is a diagram illustrating a situation example of the C-directionmapping. As shown in FIG. 23, in this case, only the saturationdirection is compressed, but the luminance direction is not compressed.That is to say, pixels mapped onto the same virtual clip boundary(V-boundary) 191 (i.e., mapping destination) have a mutually differentluminance value, so are mapped in a mutually different position. That isto say, a pixel to be processed corresponds to the mapping destinationthereof one on one. Accordingly, in FIG. 23, only an example in thecompression direction is shown, but the C-direction mapping may beapplied to the enlargement direction (reversible). The C-directionmapping has an advantage in the compression direction wherein colors areeliminated, and has an advantage in the enlargement direction whereincolors are remained.

Now, description will be back to FIG. 22. In step S123, theCusp-direction mapping processing unit 123 performs mapping processingwherein the YC coordinates are moved (mapped) onto the virtual clipboundary (V-boundary) 191 in a rectilinear direction connecting a point(Ycp, 0) and a pixel to be processed.

FIG. 24 is a diagram illustrating a situation example of Cusp-directionmapping. As shown in FIG. 24, in this case, a pixel to be processed ismapped onto the virtual clip boundary (V-boundary) 191 with a point(Ycp, 0) on the luminance (Y) axis having the same luminance value asthat of the Cusp point as a convergent point. Accordingly, in this caseas well, pixels to be mapped onto the same virtual clip boundary(V-boundary) 191 (i.e., mapping destination) are mapped in a mutuallydifferent position. Accordingly, in FIG. 24, only an example in thecompression direction is shown, but the Cusp-direction mapping may beapplied to the enlargement direction (reversible). The Cusp-directionmapping has an advantage in the compression direction wherein colors areremained to some extent, and has an advantage in the enlargementdirection wherein colors are eliminated to some extent.

Now, description will be back to FIG. 22. Upon the C-direction mappingprocessing and Cusp-direction mapping processing being completed, theprocessing proceeds to step S126.

Also, in a case wherein determination is made in step S121 that only thecompression processing is performed regarding the input picture contentdata to be subjected to color gamut conversion, and the enlargementprocessing is not performed, the combination selecting unit 121 selectsthe C-direction mapping processing unit 122 and BW-direction mappingprocessing unit 124, and advances the processing to step S124.

In step S124, the C-direction mapping processing unit 122 executes theC-direction mapping processing in the same way as in the case of stepS122.

In step S125, the BW-direction mapping processing unit 124 performsmapping processing wherein in a case in which the luminance of a pixelto be processed is brighter than the luminance of the Cusp point, thepixel to be processed is moved (mapped) onto the virtual clip boundary(V-boundary) 191 in a rectilinear direction connecting a black point andthe pixel to be processed, and in a case in which the luminance of thepixel to be processed is darker than the luminance of the Cusp point,the pixel to be processed is moved (mapped) onto the virtual clipboundary (V-boundary) 191 in a rectilinear direction connecting a whitepoint and the pixel to be processed.

FIG. 25 is a diagram illustrating a situation example of theBW-direction mapping. As shown in FIG. 25, in this case, a pixel to beprocessed which is brighter than the Cusp point is mapped onto thevirtual clip boundary (V-boundary) 191 with a black point as aconvergent point, and a pixel to be processed which is darker than theCusp point is mapped onto the virtual clip boundary (V-boundary) 191with a white point as a convergent point. In this case, all of thepixels to be processed disposed in a portion filled with slanting linesin FIG. 25 are mapped onto the Cusp point. Accordingly, this method isavailable only in the case of the compression direction, and is notunavailable in the enlargement direction (irreversible). Of theabove-mentioned three fixed mapping methods, the BW-direction mapping ismapping wherein colors are remained most, as compression-directionmapping.

Now, description will be back to FIG. 22. Upon the C-direction mappingprocessing and BW-direction mapping processing being ended, theprocessing proceeds to step S126.

In step S126, the synthesis processing unit 125 blends the mappingresults in the two mapping directions, performed in steps S122 and S123,or in steps S124 and S5125, based on a blend function.

With the above-mentioned three fixed mapping methods, as shown in FIG.26, the mapping directions differ mutually. In FIG. 26, a white circledenotes an example of a pixel to be processed, Pc denotes a mappingdestination example of the pixel to be processed according to theC-direction mapping, Pcp denotes a mapping destination example of thepixel to be processed according to the Cusp-direction mapping, and Pbwdenotes a mapping destination example of the pixel to be processedaccording to the BW-direction mapping.

In order to determine a final mapping direction, the synthesisprocessing unit 125 blends at least the two selected by the combinationselecting unit 121, of the multiple fixed mapping directions of whichthe directions differ mutually. At this time, two mapping directions ofwhich the properties differ, such as a direction for remaining colors,and a direction for eliminating colors, are blended, whereby thesynthesis processing unit 125 can adjust a desired mapping directionaccording to the blended ratio thereof. In the case of theabove-mentioned three fixed mapping directions, as described above, thefollowing two methods can be conceived, for example.

That is to say, there are a method for synthesizing the C-directionmapping and BW-direction mapping (steps S124 and S125), and a method forsynthesizing the C-direction mapping and Cusp-direction mapping (stepsS122 and S123). The combination selecting unit 121 selects whichcombination is employed depending on whether or not there is conversionin the enlargement direction.

The method for synthesizing the C-direction mapping and BW-directionmapping is a combination of two mapping directions wherein theproperties for eliminating colors and the properties for remainingcolors differ most, so adjustment can be readily made (adjustable rangeis wide). In particular, with regard to the BW-direction mapping, colorsare remained with a deeper hue, so contrast adjustment width is verywide, and accordingly, an image can be adjusted to obtain more naturalappearance. However, the BW-direction mapping is in an irreversiblemapping direction, and is accordingly prevented from being employed forthe enlargement processing.

On the other hand, in the case of synthesizing the C-direction mappingand Cusp-direction mapping, the properties of the Cusp-direction mappingis somewhat ambiguous as compared to the BW-direction mapping, anadjustable range in the case of color gamut compression or the like isnarrower as compared to the case of synthesizing the C-direction mappingand BW-direction mapping. An image which is a compression result alsohas an appearance with insufficient contrast in some cases as comparedto the case of synthesizing the C-direction mapping and BW-directionmapping. However, the combined mapping directions are both reversible,and can also be employed for the enlargement processing.

That is to say, in general, in the case of performing color gamutcompression alone, the method for synthesizing the C-direction mappingand BW-direction mapping can obtain a more natural appearance result ascompared to the method for synthesizing the C-direction mapping andCusp-direction mapping, but in the event of performing color gamutenlargement, the method for synthesizing the C-direction mapping andCusp-direction mapping can obtain a more desirable result.

In general, in order to approximate to an ideal clip direction, thecombination selecting unit 121 defines at least two types of fixedmapping directions, but as shown in FIG. 27, mapping (direction A)wherein only the saturation direction is compressed, and colors areeliminated is taken as one of the fixed mapping directions, and mapping(direction B) wherein both of the saturation direction and luminancedirection are moved, and colors are remained is taken as the other. Afinal mapping direction is determined by the synthesis processing unit125 blending the two directions with an appropriate ratio. With theexample in FIG. 27, the directions A and B are blended with a ratio of1:2. That is to say, if the blend ratio between the fixed mappingdirections can be defined appropriately for each pixel to be processed,mapping can be performed so as to approximate to an ideal mappingdirection. Therefore, the synthesis processing unit 125 performs mappingby employing a blend function wherein a mixed ratio is specified foreach hue.

An example of such a blend function is shown in FIG. 28. In the case ofthis blend function, as to a color gamut 300 shown in the left side ofFIG. 28, the use ratio of the C-direction mapping point is exhibitedregarding a pixel to be processed of which the luminance is around awhite or black point such as an area A shown with both arrows 301 andboth arrows 302 shown in the center of FIG. 28, and the use ratio of theBW-direction mapping point is exhibited regarding a pixel to beprocessed of which the luminance (curve 305 on the right side of FIG.28) is around the Cusp such as an area B shown with both arrows 303. Asshown in the right side of FIG. 28, upon a blend function such as acurve 305 is given to one of the two mapping directions to be blended, avalue obtained by subtracting the value shown in the curve 305 from avalue “1.0”, i.e., a curve 304 is given to the other mapping directionas a blend function.

Note that, this blend function may be defined so as to blend two mappingdirections such as shown in FIG. 28, or three mapping directionsincluding the Cusp-direction mapping. Consequently, this blend functionis defined by adjusting this so as to realize a mapping direction suchas shown in FIG. 28.

With regard to the blend functions shown in the curves 304 and 305 suchas shown in the upper stage 311 in FIG. 29, in reality, as shown in themiddle stage 312 in FIG. 29, two types of blend functions (curves 321and 322) are prepared wherein only a BW-direction use ratio is defined,for example. One (curve 322) is a function corresponding to a pixel tobe processed on a brighter side than the Cusp point, and the other(curve 321) is a function corresponding to a pixel to be processed on adarker side than the Cusp point. Let us say that the horizontal axis ofthe blend function (graph) shown in the middle stage 312 representsluminance wherein the luminance of the Cusp point through a white point,the luminance of the Cusp point through a black point are normalizedwith 0.0 through 1.0, respectively. Note that a C-direction use ratiocan be obtained by subtracting the BW-direction use ratio from 1.0.

The luminance and saturation of the Cusp point of a color gamut differsignificantly depending on a hue, for example, such as shown in a curve351 in the graph in the upper stage of FIG. 30, or the like, and theshape of the color gamut is also accordingly changed (color gamut 361Athrough 367A in the middle stage in FIG. 30). Accordingly, the blendfunction is desirable to be changed depending on a hue, and is definedsuch as shown in the middle stage 312 in FIG. 29, whereby the synthesisprocessing unit 125 can change the blend function appropriately for eachhue in accordance with the luminance position of the Cusp point of thecolor gamut. For example, situations of the blend function at hues A andB wherein the luminance of the Cusp point is lower or higher are shownin the upper stage 311 and lower stage 313 in FIG. 29, respectively.There can be confirmed situations wherein the blend function is changedin accordance with the luminance of the Cusp point. Thus, upon changingthe blend function, even if a color gamut shape is changed for each hueas shown in the middle stage in FIG. 30, such as color gamut 362Bthrough color gamut 367B shown in the lower stage of FIG. 30, adirection wherein colors are eliminated around a white or black point,and a direction wherein colors are remained around the Cusp point, i.e.,an ideal mapping direction can be realized.

As described above, let us say that the blend function is referenced byemploying the luminance Yi of a pixel to be processed, and the obtainedBW-direction use ratio is taken as UseR_BW. A final mapping pointPout(Yo, Co) can be calculated such as the following Expressions (7) and(8) by employing a C-direction mapping point (Yc, Cc), and BW-directionmapping point (Ybw, Cbw).Yo=UseR_BW×Ybw+(1.0−UseR_BW)×Yc  (7)Co=UseR_BW×Cbw+(1.0−UseR_BW)×Cc  (8)

Now, description will be back to FIG. 22. In step S127, the formatconversion unit 126 converts the format of output content data, forexample, from the YCH to YCC. The format conversion unit 126 employs thefollowing Expressions (9) through (12) to convert the YC coordinatesPout(Yo, Co) of the obtained final mapping point from the YCHcoordinates to YCC coordinates, and calculates the YCC coordinates Pout(Yo, Cbo, Cro) of the final mapping point.Ho=Hi  (9)Yo=Yo  (10)Cbo=Co×cos(Ho)  (11)Cro=Co×sin(Ho)  (12)

Upon the processing in step S127 being completed, the blend mappingprocessing is ended, the processing is returned to step S106 in FIG. 5,and the color gamut conversion processing is ended.

As described above, with the color gamut conversion, multiple mappingdirections which differ mutually are blended with an appropriate ratioto determine a final mapping direction, whereby the color conversiondevice 100 can realize mapping direction control with higherflexibility, and can readily realize a more appropriate mappingdirection according to a purpose.

Description has been made so far wherein three examples of fixed mappingdirections are exemplified, and the mapping processing unit 114 selectstwo therefrom to synthesize these, but the fixed mapping direction maybe another direction other than the above-mentioned directions. Also,the number of fixed mapping directions to be prepared may be four ormore. Further. the mapping processing unit 114 may synthesize multiplefixed mapping directions with a combination other than theabove-mentioned combinations. For example, the mapping processing unit114 may select and synthesize three or more mapping directions.

Also, description has been made so far wherein mapping directions to besynthesized are selected by the mapping processing unit 114 depending onwhether to perform the color gamut enlargement, but a selectioncondition of mapping directions may be any condition, and mappingdirections to be selected according to each condition is arbitrary aslong as there is no inconvenience. For example, with the flowchart inFIG. 22, description has been made wherein in a case in which the colorgamut enlargement is not performed, the C-direction mapping andBW-direction mapping are selected and synthesized, but the presentinvention is not restricted to this, other mapping directions may beselected. For example, even in a case wherein the color gamutenlargement is not performed, the mapping processing unit 114 may selectthe C-direction mapping and Cusp-direction mapping according to a colorgamut or the like of an output device.

That is to say, any kind of method may be employed as long as the methodcan select a color gamut appropriately in accordance with apredetermined condition, and also, conditions for selecting each method,and the number of directions to be synthesized are arbitrary.

Information processing system examples employing a color gamutconversion method such as described above are shown in FIGS. 31A and31B.

The respective information processing systems shown in FIGS. 31A and 31Bare information processing systems to which an embodiment of the presentinvention has been applied. The color gamut conversion such as describedabove is performed in the case of picture content data being exchangedbetween multiple devices, or in the case of expecting picture contentdata to be exchanged between multiple devices. With regard to acombination of devices to perform exchange of picture content data, andthe exchange method thereof, there can be conceived various combinationsand various methods, but in FIGS. 31A and 31B, description will be maderegarding a case wherein with an information processing systemconfigured of a supply-side device 401 for supplying picture contentdata, and an obtaining-side device 402 for obtaining the picture contentdata, the color gamut conversion is performed, for convenience ofexplanation.

FIG. 31A illustrates an example in the case of performing the colorgamut conversion at the obtaining-side device 402. As shown in FIG. 31A,the supply-side device 401 supplies input picture content data 411 andoriginal color gamut information 412 to the obtaining-side device 402.The obtaining-side device 402 has the same function as that of the colorgamut conversion device 100 in FIG. 3, includes a color gamut conversionunit 421 for performing similar processing, and has further obtainedtarget color gamut information 422. The color gamut conversion unit 421performs color gamut conversion based on the original color gamutinformation 412 supplied from the supply-side device 401, and the targetcolor gamut information 422 to convert the input picture content data411 supplied from the supply-side device 401 into output picture contentdata 423.

FIG. 31B illustrates another example in the case of performing the colorgamut conversion at the supply-side device 401. As shown in FIG. 31B,the supply-side device 401 includes the color gamut conversion unit 421,and has obtained the input picture content data 411 and original colorgamut information 412. Also, the obtaining-side device 402 supplies thetarget color gamut information 422 to the supply-side device 401. Thecolor gamut conversion unit 421 performs color gamut conversion based onthe original color gamut information 412, and the target color gamutinformation 422 supplied from the obtaining-side device 402 to convertthe input picture content data 411 into output picture content data 423.The supply-side device 401 supplies the converted output picture contentdata 423 to the obtaining-side device 402.

As described above, the present invention may be applied to any kind ofdevice as long as the device has the same configuration as that of thecolor gamut conversion device 100 in FIG. 1, and includes the colorgamut conversion unit 421 for performing similar processing. That is tosay, for example, as described with reference to FIG. 31, the colorgamut conversion unit 421 can select an appropriate color gamutconversion method according to a device and conditions, and can performcolor gamut conversion appropriately according to more variousconditions.

The above-mentioned series of processing can be executed not only byhardware but also by software. In this case, for example, theabove-mentioned series of processing may be configured as a personalcomputer such as shown in FIG. 32.

In FIG. 32, a CPU (Central Processing Unit) 501 of a personal computer500 executes various types of processing in accordance with a programstored in ROM (Read Only Memory) 502, or a program loaded into RAM(Random Access Memory) 503 from a storing unit 513. Data or the likeused by the CPU 501 to execute various types of processing is alsostored in the RAM 503 as appropriate.

The CPU 501, ROM 502, and RAM 503 are mutually connected through a bus504. An input/output interface 510 is also connected to the bus 504.

The input/output interface 510 is connected with an input unit 511 madeup of a keyboard, mouse, and so forth, a display made up of CRT (CathodeRay Tube), LCD (Liquid Crystal Display), or the like, an output unit 512made up of a speaker and so forth, a storing unit 513 configured of ahard disk or the like, and a communication unit 514 configured of amodem or the like. The communication unit 514 performs communicationprocessing through a network including the Internet.

The input/output interface 510 is also connected with a drive 515 asappropriate, on which a removable medium 521 such as a magnetic disk,optical disc, magneto-optical disk, semiconductor, or the like ismounted as appropriate, and a computer program read out therefrom isinstalled into the storing unit 513 as appropriate.

In a case wherein the above-mentioned series of processing is executedby software, a program making up the software thereof is installed froma network or recording medium.

The recording medium is not restricted to being configured of,separately from the device main unit such as shown in FIG. 32 forexample, the removable medium 521 made up of a magnetic disk (includinga flexible disk), optical disc (including CD-ROM (Compact Disc-Read OnlyMemory), DVD (Digital Versatile Disc)), magneto-optical disk (includingMD (Mini Disc)), semiconductor memory, or the like, wherein a program tobe distributed to a user is recorded, but also may be the ROM 502, ahard disk included in the storing unit 513, or the like, wherein aprogram to be distributed to a user in a state built into a device mainunit beforehand is recorded.

Note that, with the present Specification, steps describing a program tobe recorded in a recording medium include not only processing performedin time series along a described order but also processing executed inparallel or individually even though not necessarily performed in timeseries.

Also, with the present Specification, the term “system” represents theentirety of equipment configured of multiple devices.

Note that the configuration described above as a single device may beconfigured as multiple devices. Conversely, the configuration describedabove as multiple devices may be configured as a single devicecollectively. Also, a configuration other than the above-mentionedconfiguration may be added to the configuration of each device. Further,if the configuration and operation as the entire system aresubstantially the same, a part of the configuration of a certain devicemay be included in another device. That is to say, embodiments of thepresent invention are not restricted to the above-mentioned embodiment,and various changes can be made without departing from the essence andspirit of the present invention.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

What is claimed is:
 1. An information processing device configured toperform color gamut conversion for compressing or enlarging the colorgamut of image data, comprising: selecting means configured to select aplurality of coordinate movement directions to be synthesized fordetermining the coordinate movement destination of a pixel to beprocessed during said color gamut conversion; coordinate moving meansconfigured to move the coordinates of said pixel to be processed in eachof the selected plurality of directions; and synthesizing meansconfigured to synthesize coordinate movement in the selected pluralityof directions, wherein color gamut conversion is performed according tooriginal color gamut information and target color gamut information, andwherein the original color gamut information and the target color gamutinformation is generated according to a cusp table which is renderedaccording to one of an index and xy chromaticity data of three primarycolors, wherein said selecting means select selects a plurality of saidcoordinate movement directions based on regarding whether or not colorgamut enlargement processing for enlarging a color gamut is performed assaid color gamut conversion, wherein said selecting means select selectsa saturation direction, and a rectilinear direction which connects ablack point or white point and said pixel to be processed as saidcoordinate movement directions in a case wherein said color gamutenlargement processing is not performed, and select selects a saturationdirection, and a rectilinear direction which connects a point, which isdisposed on a luminance axis, having the same luminance value as that ofthe maximum saturation point, and said pixel to be processed as saidcoordinate movement directions in a case wherein said color gamutenlargement processing is performed.
 2. An information processing deviceconfigured to perform color gamut conversion for compressing orenlarging the color gamut of input image data, comprising: selectingunit configured to select a plurality of coordinate movement directionsto be synthesized for determining the coordinate movement destination ofa pixel to be processed during said color gamut conversion; coordinatemoving unit configured to move the coordinates of said pixel to beprocessed in each of the selected plurality of directions; andsynthesizing unit configured to synthesize coordinate movement in theselected plurality of directions so as to generate synthesized imagedata, wherein color gamut conversion is performed according to originalcolor gamut information and target color gamut information, and whereinthe original color gamut information and the target color gamutinformation is generated according to a cusp table which is renderedaccording to one of an index and xy chromaticity data of three primarycolors, wherein said selecting unit selects a plurality of saidcoordinate movement directions based on whether or not color gamutenlargement processing for enlarging a color gamut is performed as saidcolor gamut conversion, wherein said selecting unit selects a saturationdirection, and a rectilinear direction which connects a black point orwhite point and said pixel to be processed as said coordinate movementdirections in a case wherein said color gamut enlargement processing isnot performed, and selects a saturation direction, and a rectilineardirection which connects a point, which is disposed on a luminance axis,having the same luminance value as that of the maximum saturation point,and said pixel to be processed as said coordinate movement directions ina case wherein said color gamut enlargement processing is performed. 3.The information processing device according to claim 2, wherein saidcoordinate moving unit moves said pixel to be processed in therectilinear direction which connects the black point and said pixel tobe processed in a case wherein the luminance of said pixel to beprocessed is brighter than the luminance of the maximum saturationpoint, and moves said pixel to be processed in the rectilinear directionwhich connects the white point and said pixel to be processed in a casewherein the luminance of said pixel to be processed is darker than theluminance of the maximum saturation point.
 4. The information processingdevice according to claim 2, wherein said synthesizing unit synthesizescoordinate movement performed in the selected plurality of directionswith a ratio based on a blend function.
 5. The information processingdevice according to claim 4, wherein the blend function changesdepending on a hue.
 6. The information processing device according toclaim 2, wherein the input image data and the synthesized image data area YCH format.
 7. The information processing device according to claim 6,further comprising: a format conversion unit configured to convert thesynthesized image data from the YCH format into a YCC format.
 8. Aninformation processing method to perform color gamut conversion forcompressing or enlarging the color gamut of input image data, comprisingthe steps of: selecting a plurality of coordinate movement directions tobe synthesized for determining the coordinate movement destination of apixel to be processed during said color gamut conversion; moving thecoordinates of said pixel to be processed in each of the selectedplurality of directions; and synthesizing, by a processor, coordinatemovement in the selected plurality of directions so as to generatesynthesized image data, wherein color gamut conversion is performedaccording to original color gamut information and target color gamutinformation, and wherein the original color gamut information and thetarget color gamut information is generated according to a cusp tablewhich is rendered according to one of an index and xy chromaticity dataof three primary colors, wherein a plurality of said coordinate movementdirections are selected based on whether or not color gamut enlargementprocessing for enlarging a color gamut is performed as said color gamutconversion, wherein a saturation direction, and a rectilinear directionwhich connects a black point or white point and said pixel to beprocessed as said coordinate movement directions are selected in a casewherein said color gamut enlargement processing is not performed, and asaturation direction, and a rectilinear direction which connects apoint, which is disposed on a luminance axis, having the same luminancevalue as that of the maximum saturation point, and said pixel to beprocessed as said coordinate movement directions are selected in a casewherein said color gamut enlargement processing is performed.
 9. Theinformation processing method according to claim 8, wherein said pixelto be processed is moved in the rectilinear direction which connects theblack point and said pixel to be processed in a case wherein theluminance of said pixel to be processed is brighter than the luminanceof the maximum saturation point, and said pixel to be processed is movedin the rectilinear direction which connects the white point and saidpixel to be processed in a case wherein the luminance of said pixel tobe processed is darker than the luminance of the maximum saturationpoint.
 10. The information processing method according to claim 8,wherein coordinate movement performed in the selected plurality ofdirections are synthesized with a ratio based on a blend function. 11.The information processing device according to claim 10, wherein theblend function changes depending on a hue.
 12. The informationprocessing method according to claim 8, wherein the input image data andthe synthesized image data are a YCH format.
 13. The informationprocessing method according to claim 12, further comprising the stepsof: converting the synthesized image data from the YCH format into a YCCformat.
 14. A non-transitory computer readable recording medium havingstored thereon a program enabling a computer to execute an informationprocessing method to perform color gamut conversion for compressing orenlarging the color gamut of input image data, the method comprising thesteps of: selecting a plurality of coordinate movement directions to besynthesized for determining the coordinate movement destination of apixel to be processed during said color gamut conversion; moving thecoordinates of said pixel to be processed in each of the selectedplurality of directions; and synthesizing coordinate movement in theselected plurality of directions so as to generate synthesized imagedata, wherein color gamut conversion is performed according to originalcolor gamut information and target color gamut information, and whereinthe original color gamut information and the target color gamutinformation is generated according to a cusp table which is renderedaccording to one of an index and xy chromaticity data of three primarycolors, wherein a plurality of said coordinate movement directions areselected based on whether or not color gamut enlargement processing forenlarging a color gamut is performed as said color gamut conversion,wherein a saturation direction, and a rectilinear direction whichconnects a black point or white point and said pixel to be processed assaid coordinate movement directions are selected in a case wherein saidcolor gamut enlargement processing is not performed, and a saturationdirection, and a rectilinear direction which connects a point, which isdisposed on a luminance axis, having the same luminance value as that ofthe maximum saturation point, and said pixel to be processed as saidcoordinate movement directions are selected in a case wherein said colorgamut enlargement processing is performed.
 15. The non-transitorycomputer readable recording medium according to claim 14, wherein saidpixel to be processed is moved in the rectilinear direction whichconnects the black point and said pixel to be processed in a casewherein the luminance of said pixel to be processed is brighter than theluminance of the maximum saturation point, and said pixel to beprocessed is moved in the rectilinear direction which connects the whitepoint and said pixel to be processed in a case wherein the luminance ofsaid pixel to be processed is darker than the luminance of the maximumsaturation point.
 16. The non-transitory computer readable recordingmedium according to claim 14, wherein coordinate movement performed inthe selected plurality of directions are synthesized with a ratio basedon a blend function.
 17. The non-transitory computer readable recordingmedium according to claim 16, wherein the blend function changesdepending on a hue.
 18. The non-transitory computer readable recordingmedium according to claim 14, wherein the input image data and thesynthesized image data are a YCH format.
 19. The non-transitory computerreadable recording medium according to claim 18, the method furthercomprising the steps of converting the synthesized image data from theYCH format into a YCC format.